Items allegedly carried by Ryan Fogle, a third secretary at the U.S. Embassy in Moscow, when he was detained by Russia's FSB, are shown in FSB offices in Moscow, May 14, 2013.

FSB/CBS

The FSB, which is the successor to the Soviet-era KGB, said Fogle was trying to recruit a Russian counterterrorism officer who specializes in the Caucasus, a region in southern Russia that includes Chechnya and Dagestan. The suspects in the Boston Marathon bombings are ethnic Chechen brothers and the elder brother spent six months last year in Dagestan, now the center of an Islamic insurgency.

U.S. investigators have been working with the Russians to try to determine whether Tamerlan Tsarnaev had established any contacts with the militants operating in Dagestan.

The purported Russian-issued diplomatic ID card of a U.S. man identified by Russian security services as Ryan Christopher Fogle.

RT

The detention of Fogle appeared to be the first case of an American diplomat publicly accused of spying in about a decade and seemed certain to put further strain on relations between the two countries.

In another twist to the story, Russian state television aired video Wednesday provided by Russia's security services claiming that another alleged American spy was expelled earlier in 2013. In the clip, a man identified only as an FSB operative and sitting in near darkness said a "CIA operative" was expelled in January. He said the FSB then asked its U.S. counterparts to halt this "disturbing activity."

The man also claimed the Russians had been shadowing Fogle since he began his Moscow posting in 2011. There was no way to independently verify who the man speaking in the video was.

Neither the U.S. Embassy in Moscow nor the State Department has made any official comment on the accusations against Fogle, or on the newly reported case Wednesday.

After being arrested and processed by Russian security services, Fogle was handed back to the U.S. diplomatic mission in Moscow on Tuesday. Fogle was declared persona non grata and ordered to leave Russia immediately, the Foreign Ministry said. He has diplomatic immunity, which protects him from arrest.

The FSB claims Fogle was masquerading as a career diplomat at the Political Section of the U.S. Embassy, but that he was in fact a CIA employee.

Noting recent efforts by the two countries to improve cooperation in countering international terrorism in the wake of the Boston bombings, the Foreign Ministry said "such provocative actions in the spirit of the Cold War do nothing to strengthen mutual trust."

Despite the end of the Cold War, Russia and the United States still maintain active espionage operations against each other. Last year, several Russians were convicted in separate cases of spying for the U.S. and sentenced to lengthy prison sentences.

Russian state television showed pictures of a man said to be Fogle, wearing a baseball cap and what appeared to be a blond wig, lying face down on the ground. The man, now without the wig, was also shown sitting at a desk in the offices of the FSB. Two wigs, a compass, a map of Moscow, a pocket knife, three pair of sunglasses and packages of 500 euro notes were among the items displayed on a table.

In an image from video released by the Russian FSB spy agency on May 14, 2013, three U.S. Embassy officials are seen next to Ryan Fogle (seated at right), who was detained by the FSB on accusations of espionage.

FSB/Handout

The FSB later released video of the arrest and the subsequent lecturing of three U.S. officials from the Political Section of the U.S. Embassy who came to retrieve Fogle.

Unidentified Russian officials first explain the accusations against Fogle to the American diplomats before criticizing the U.S. for the alleged offense: "When our countries have achieved a new level of mutual relations, when our presidents are trying to improve the climate of understanding on the government level, this citizen on behalf of the U.S. government commits the most serious crime here in Moscow. Do you have any questions, gentlemen?"